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Fold the arcs A B and B C round the arcs B D E, B F E, and make the sides A G and C H coincide every where together upwards from the point E, which will represent a cone cut obliquely to its base, and shew the section to be an ellipsis.






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I. Form the whole part of the cone A C B, by bringing the points A and B together, and bending it so as to become round as near as may be.
II. Bend regularly the other part of the figure, so that the arcs D E, F E, may surround the arcs F G, F H.
III. Raise up the parabola G I H, making the point I meet the coincident points A and B; thus may you see the section made by cutting a cone parallel to one of its sides.






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The last directions (Plate XLI) obtain here; for bringing E and F together, and rounding the part E D E, as was there described, and the points A and B being brought to G and H, if the hyperbola G I H be then raised up, as before directed, the section of a cone, cut parallel to its axis, will be thereby presented to view.